noun, plural: lanugos
Lanugo is hair that is thin, soft, poorly pigmented, and lacking in central medulla.1 In humans and other mammals, lanugo is the type of hair that covers the body of the fetus or a newborn. It is the first type of hair produced by the hair follicles. In humans, it begins to appear around 16 weeks of gestation. It is believed to serve as an anchor to hold the vernix caseosa (i.e. a waxy, white coat) on the skin of the fetus.
Lanugo is typically shed before birth, typically at about 33 to 36 weeks of gestation. However, it may persist even after birth and therefore the newborn may be seen covered with lanugo. When this happens, the lanugo is soon shed within a few weeks.
Lanugo is replaced by another type of hair called vellus hair, which is thinner than the former.
Word origin: Latin lānūgō (down, wooliness), from lana (wool)
- primary hair
- downy hair
- lanuginous (adjective, covered with lanugo)
1 Peytavi, U. (2008). Hair growth and disorders. Berlin: Springer. p.9